1. Technical Field
The present disclosure relates to a vehicle control apparatus for controlling an inter-vehicle distance between a vehicle carrying the apparatus and a preceding vehicle.
2. Related Art
A vehicle control apparatus is known that is configured to control an inter-vehicle distance between a vehicle carrying the apparatus (hereinafter referred to as a subject vehicle) and a preceding vehicle. Such a vehicle control apparatus may use a radar device to calculate a distance to the preceding vehicle and a relative speed of the preceding vehicle. The radar device is configured to transmit radar waves to the front of the subject vehicle and receive reflected waves from a target present forward of the subject vehicle, and calculate a distance to the target and a relative speed and a lateral position of the target to generate target information about the target.
The vehicle control apparatus is configured to, based on the target information, identify a target that is closest to the subject vehicle among a plurality of targets as a preceding vehicle, and control travel of the subject vehicle to bring the inter-vehicle distance between the subject vehicle and the preceding vehicle to a preset target inter-vehicle distance.
At a decreased distance from the preceding vehicle, the radar device may fail to detect a target corresponding to the rear end of the preceding vehicle. For example, in a case where the preceding vehicle is a large vehicle having the rear end at an elevated position, approach of the subject vehicle and the preceding vehicle may cause “underriding” or the like in some mounting conditions of the radar-device on the vehicle front, which refers to an event that the radar waves travel beneath a chassis of the like of the preceding vehicle. In such a case, a forward portion, rather than the rear end, of the preceding vehicle may be incorrectly identified as a target of the preceding vehicle that is closest to the subject vehicle.
Implementation of the inter-vehicle distance control of the subject vehicle behind such an incorrectly identified target may lead to an event that the inter-vehicle distance between the rear end of the preceding vehicle and the subject vehicle rapidly decreases as compared to the target inter-vehicle distance.
To prevent such failure, a known technique disclosed in Japanese Patent Application Laid-Open Publication No. 2004-330890 is configured to correct the inter-vehicle distance between the preceding vehicle and the subject vehicle. Such a technique is configured to, when a difference between previous and current values of the inter-vehicle distance increases above a predetermined value, determine that the underriding has occurred, store the difference between previous and current values of the inter-vehicle distance as an offset, and subtract the offset from the current value of the inter-vehicle distance, thereby enabling the inter-vehicle distance control to be implemented behind the rear end of the preceding vehicle even when the rear end of the preceding vehicle fails to be detected as a target.
However, the technique disclosed in Japanese Patent Application Laid-Open Publication No. 2004-330890 does not take into account a case that the preceding vehicle and the subject vehicle becomes spaced apart from each other. Therefore, there is room for improvement in the inter-vehicle distance control such that the inter-vehicle distance between the rear end of the preceding vehicle and the subject vehicle can be controlled to the preset target inter-vehicle distance also in such a case.
In consideration of the foregoing, exemplary embodiments of the present disclosure are directed to providing a vehicle control apparatus capable of properly implementing inter-vehicle distance control of a vehicle carrying the apparatus behind a preceding vehicle.